Conventional earth boring bits have an integral threaded pin for attachment of the bit to a drill string. The screw threads of the threaded pin and of the drill string have an orientation such that the various connections all tend to be tightened by the rotary motion of the bit during drilling operation. If the bit was not properly tightened at installation, this tends to result in over tightening of the drill bit to the drill string. When the over-tightened bit is expended there may be significant difficulty in removing the bit from the drill string. Various techniques have been used to remove an over-tightened bit including use of an oxygen/acetylene torch to heat the threaded connection in an attempt to release the over-tightened bit from the drill string. This is a time consuming operation and many times results in significant down time for a rig. Another often used technique is to use a sledge hammer in an attempt to loosen the drill bit from the over-tightened condition. This bit removal problem has always been a serious one and very little effort has been directed to finding an acceptable solution.
U.S. Pat. No. 5,234,063 describes a break-out ring for mounting on a circular surface of a drill bit at the connecting pin to facilitate removal of the over-tightened bit from the drill string. However, the break-out ring described in this United States patent has parallel surfaces and when assembled between a shoulder of the drill bit and a special bit sub required for installation of the drill bit there is little improvement for removal of the bit. The break-out ring of this patent is described as having weakened portions to facilitate removal of the ring thereby releasing the over-tightened drill bit from the drill string. Because of the parallel surfaces of the break-out ring there is considerable difficulty in removing the ring to release the over-tightened drill bit. The parallel surfaces of the break-out ring becomes a part of the over-tightened connection and requires considerable force for removal from between the drill bit and the drill string.
Thus there is a need for a breakable washer for assembly between a drill bit and the standard connection of a drill string that enables removal of a drill bit in an over-tightened condition without destruction of the drill bit, and with relative ease.